Liquid supply apparatus



June 6, 1 967 5, TYLER I 3,323,463

LIQUID SUPPLY APPARATUS Filed Feb. 18. 1965 INVENTOR S774AILEy 75. 771.51

A-r-roepav United States Patent M 3,323,463 LIQUID SUPPLY APPARATUS Stanley R. Tyler, Cheltenham, England, assignor to Dowty Fuel Systems, Limited Filed Feb. 18, 1965, Ser. No. 433,637 Claims priority, application Great Britain, Mar. 9, 1964, 9,869/ 64 4 Claims. (Cl. 103-97) ABSTRACT OF THE DISCLOSURE Liquid supply apparatus having a variable delivery pump with a throttle valve in its delivery, the opening of which is varied in response to the magnitude of a control signal, and a servomotor which varies the delivery of the pump under the control of spring means, and in response to a change in pressure difference across the throttle valve so as to maintain said pressure difference substantially constant for a given load of the spring means, wherein the load of the spring means is varied by the movable member of the throttle valve so as to vary the pressure difference across the throttle valve in accordance with the extent of opening of said valve.

Field of the invention: This invention relates to liquid supply apparatus and more particularly, although not exclusively, to the supply of liquid fuel to a gas turbine engine.

Summary of the invention: In accordance with the present invention, a liquid supply apparatus comprises a variable delivery pumping assembly including flowvarying means, an adjustable throttle opening through which the pump delivery is arranged to pass, adjusting means arranged to vary the throttle opening in accordance with a controlling signal, means responsive to the fluid pressure across the throttle opening, said means being operable on the flow-varying means to vary the delivery of the pumping assembly with effect to maintain the fluid pressure across the throttle opening at a controlled value, and pressure-regulating means operable by the throttle adjusting means to increase the value of the controlled pressure as the throttle opening increases.

Brief description of the drawing: An embodiment of the invention, for use in the supply of liquid fuel to a gas turbine engine, is illustrated in the accompanying diagrammatic drawing.

Description of the preferred embodiment: In this drawing the pumping assembly comprises a centrifugal pump 1 fed with liquid fuel at a low pressure at its inlet 2, and a valve 3in the inlet serving in conjunction with the low pressure from the inlet 2 to determine the liquid flow rate into the pump. The arrangement of the centrifugal pump -1 is such that by virtue of its size and driving speed the liquid fuel which it receives takes the form of an annulus around the periphery of the pump whose radial depth determined delivery pressure. The arrangement of this pump may be as disclosed in United States specification Ser. No. 3,128,822.

The pump inlet valve 3 is adjusted in position by a piston and cylinder actuator 4 which with the valve 3 constitute flow-varying means. The delivery passage 5 from the pumping assembly 1 carries fluid at pressure to the throttle assembly 6. This assembly comprises a cylinder 7 within which a waisted piston valve member 8 is slidably mounted. The delivery 5 is fed to a port 9 having free connection to the waisted portion of the valve member 8. A further port 11 in the cylinder 7 is adjustably closed by a land of the piston valve member 8 to form the throttle opening. Fuel leaves from the port 11 and passes through a pipe 12 to the gas turbine engine. The

3,323,463 Patented June 6, 1967 port 11 is profiled to provide a desired relationship between valve movement and the area of the opening.

From the ends of the valve member 8 rods 13 and 14 extend oppositely in sealed relation through the ends of the cylinder 7.

Means for varying the throttle opening as a function of the magnitude of the cont-rolling signal will now be described.

The endwise position of the piston valve member 8 within the cylinder 7, together forming a servo motor, is adjusted by the flow of hydraulic pressure to the two ends of the cylinder 7 through pipes 15 and 16 by a spring 17 located in one end of the cylinder 7 to act on the piston valve member. The pressures supplied to the pipes 15 and 16 are controlled by the movement of the spool of a signal valve 18 which selects the pressure supplied to the pipes 15 and 16 from pressure and return connections 19 and 21.

The spool valve 18 is controlled by a lever 22. The lever 22 is arranged to pivot about a movable fulcrum 23 which is carried by the rod 14 extending from the piston valve 8. A pair of pipes 24 and 25 carry fluid pressure signals from the gas turbine engine, such for example as compressor inlet and compressor delivery pressures, to pressure-sensitive members shown as a pair of piston and cylinder units 26 and 27. These pressures together from the controlling signal. Compression springs 28 and 29 act against opposite ends respectively of the lever 22. The spring 29 may include a fluid containing capsule 31 which compensates for local temperature variation.

For controlling the fluid actuator 4 a pair of passages 32 and 33 are connected to a control valve 30 which is operable to connect high and loW pressures from supply pipes 34 and 35 reversably to the passages 32 and 33. The valve 36 is controlled by a lever 36 pivoted on a movable fulcrum 37. The fulcrum 37 is carried by the rod 13 which extends from the valve member 8. Compression springs 38 and 39 act against opposite ends respectively of the lever 36. A pair of pressure-sensitive members 41 and 42 act oppositely on the lever 36, these members being connected to the ports 1:1 and 9 respectively of the throttle valve to form means responsive to the fluid pressure across the throttle opening.

In operation, the controlling signal represented by the pressure difierence between pipes 24 and 25 causes the pressure-sensitive members 26 and 27 to exert a net force on lever 22 which determines fuel flow. If this force and the loads of the springs 28 and 29 do not balance about the fulcrum 23, there will be movement. of the spool valve 18 which will feed pressure liquid to one or other end of the cylinder 7 to move piston valve 8 appropriately. The resulting feedback movement of the fulcrum 23 by the piston valve 8 will be in the sense to achieve balance between the force exerted bythe members 26 and 27 and the forces exerted by the springs 28 and 29. When these forces are balanced, the spool valve member will occupy a neutral position in which the passages 15 and 16 are closed.

If the flow from the pump 1 produces a pressure difference across the port 11, at which the resulting net force exerted by members 41, 42 on the lever 36 does not balance the forces exerted by the springs 38, 39 about the lever fulcrum 37, the control valve 30 will be moved from its neutral position. The piston and cylinder unit 4 is then actuated by fluid from the control valve 30 to alter the pump delivery, as controlled by the pump inlet valve 3, to a value at which the pressure difference across the port 11 restores a balance of forces about the lever fulcrum 37 with the control valve 30 in its neutral position.

By controlling both the throttle opening and the pressure drop across the throttle opening in the delivery from the variable delivery pump it is possible to control flow rate more accurately over a wide range of flow rates, especially at the lower end of the flow range. In known flow control devices having a substantially constant fluid pressure across an adjustable throttle, it has been diflicult to control fluid flow accurately at the lower end of the flow range because a small movement of the throttle valve produces a large proportional flow change. By means of the present invention the throttle opening and the fluid pressure across the throttle are simultaneously varied, whereby a given small throttle valve movement of the lower end of the flow range produces a smaller proportional flow change than that which would be produced if the fluid pressure were maintained substantially constant.

By using levers having movable fulera as shown in the illustrated embodiment, the springs are maintained at substantially constant compression in the balanced condition of the levers 22 and 36 at which the valves 18 and 30 respectively are in their neutral positions. This reduces errors in the controlled liquid flow which may arise from variation of the physical properties of the springs with temperature. It is possible to correct for such variation by arranging that one or more of the springs, for example the spring 29 as shown, shall include temperature compensating means such as the fluid-containing capsule 31. The spool valve 8 is then hydraulically locked in position to give an extent of throttle open at the port 11 which is in accordance with the pressure diflerence between pipes 24 and 25. Movement of the piston valve member 8 will also shift the fulcrum 37 to alter the proportionality between the net force exerted by the pressure-sensitive members 41 and 42 and the net force exerted by the springs 38 and 39 at which the lever 36 will maintain the spool valve 30 in its neutral position. The net force exerted by the members 41 and 42 directly depends on the rate of fluid flow delivered by the pump 1 through the throttle opening at 11 and such flow rate is adjusted by the piston and cylinder unit 4 Which in turn is controlled by the spool valve 30.

Whilst in the described embodiment the servo motor control system for adjusting both the throttle opening and for adjusting the delivery rate of the pumping assembly employs the lever and movable fulcrum technique for adjusting purposes, it will be appreciated that other arrangements are possible. For example, movement of the piston valve 8 could be used to provide variable spring bias against fluid pressure signalling devices which act directly on the respect spool valves 18 and 34.

Although the variable delivery pumping assembly has been shown in the embodiment described as an inlet con trolled centrifugal pump, other forms of variable delivery pumping are possible. For example, a variable delivery positive displacement piston pump may be employed in which the piston stroke is controlled by the servo motor 4. Again, a fixed displacement pump may be employed having a by-pass which is controlled by the servo motor 4.

I claim as my invention:

1. Liquid supply apparatus comprising (A) a variable delivery pump assembly (1) having (1) an inlet (2) for connection with a source of liquid and (2) a flow-varying member (3) which is movable to vary the flow of liquid through the pump,

(B) an adjustable throttle valve (6) interposed in a delivery conduit (5, 12) leading from the pump, said throttle valve including 4 (1) a throttling port (11) and (2) a movable member (8) which is movable to vary the opening of said throttling port (11),

(C) means (26, 27) responsive to a control signal and adapted to shift the movable member (8), and so to vary the openingof the throttling port in accordance with the magnitude of the control signal,

(D) servomotor means including (1) a servomotor (4) operable to control the flowvarying member (3) and (2) a control valve (30) for the servomotor,

(E) spring means (38, 39) operable on the control valve (30),

(F) pressure-sensitive means (41, 42) responsive to the fluid pressure difference across the throttling port (11), and operable upon the control valve (31)) in opposition to the load of the spring means to control the servomotor (4), and thus the flow-varying member (3), whereby the pump delivery is varied to maintain a pressure diflerence across the throttling port (11) which is substantially constant for a given load of the spring means, and

(G) controlling means (36, 37) operable by the movable member (8) to vary the load of the spring means (38, 39) of the control valve (30), so as to vary the maintained pressure difference across the throttling port (11) in accordance with the extent of opening of the throttling port.

2. Liquid supply apparatus according to claim 1,

wherein the controlling means comprises (A) a lever (26) which is loaded at different positions by two springs (38, 39) constituting said spring means, and

(B) a lever fulcrum (37) which is movable by the movable member (8).

3. Liquid supply apparatus according to claim 1, wherein the movable member (8) of the throttle valve is formed as a piston which is fluid-pressure controlled by a signal valve (18) under opposed valve-operating loads of (A) said signal responsive means, and of (B) a second spring means (28, 29), the load of which is varied by feedback means (22, 23) in response to movement of the movable member (8).

4. Liquid supply apparatus according to claim 3,

wherein the feedback means comprises (A) a lever (22) which is loaded at different positions by two springs (28, 29) constituting said second spring means, and

(B) a lever fulcrum (23) which is movable by the movable member (8).

References Cited UNITED STATES PATENTS 2,411,574 11/1946 Hunt 103-42 2,747,598 5/1956 Wooldridge l0321 2,829,664 4/1958 Mountford 103-21 2,889,780 6/1959 Binford 10316 2,944,488 7/1960 Meyer 10321 3,067,693 12/1962 Lambeck 103-38 3,232,238 2/1966 Faisandier 10321 DONLEY J. STOCKING, Primary Examiner.

LAURENCE V. EFNER, Examiner.

W. L. FREEH, Assistant Examiner. 

1. LIQUID SUPPLY APPARATUS COMPRISING (A) A VARIABLE DELIVERY PUMP ASSEMBLY (1) HAVING (1) AN INLET (2) FOR CONNECTION WITH A SOURCE OF LIQUID AND (2) A FLOW-VARYING MEMBER (3) WHICH IS MOVABLE TO VARY THE FLOW OF LIQUID THROUGH THE PUMP, (B) AN ADJUSTABLE THROTTLE VALVE (6) INTERPOSED IN A DELIVERY CONDUIT (5,12) LEADING FROM THE PUMP, SAID THROTTLE VALVE INCLUDING (1) A THROTTLING PORT (11) AND (2) A MOVABLE MEMBER (8) WHICH IS MOVABLE TO VARY THE OPENING OF SAID THROTTLING PORT (11), (C) MEANS (26,27) RESPONSIVE TO A CONTROL SIGNAL AND ADAPTED TO SHIFT THE MOVABLE MEMBER (8), AND SO TO VARY THE OPENING OF THE THROTTLING PORT IN ACCORDANCE WITH THE MAGNITUDE OF THE CONTROL SIGNAL, (D) SERVOMOTOR MEANS INCLUDING (1) A SERVOMOTOR (4) OPERABLE TO CONTROL THE FLOWVARYING MEMBER (3) AND (2) A CONTROL VALVE (30) FOR THE SERVOMOTOR, (E) SPRING MEANS (38, 39) OPERABLE ON THE CONTROL VALVE (30), (F) PRESSURE-SENSITIVE MEANS (41, 42) RESPONSIVE TO THE FLUID PRESSURE DIFFERENCE ACROSS THE THROTTLING PORT (11), AND OPERABLE UPON THE CONTROL VALVE (30) IN OPPOSITION TO THE LOAD OF THE SPRING MEANS TO CONTROL THE SERVOMOTOR (4), AND THUS THE FLOW-VARYING MEMBER (3), WHEREBY THE PUMP DELIVERY IS VARIED TO MAINTAIN A PRESSURE DIFFERENCE ACROSS THE THROTTLING PORT (11) WHICH IS SUBSTANTIALLY CONSTANT FOR A GIVEN LOAD OF THE SPRING MEANS, AND (G) CONTROLLING MEANS (36, 37) OPERABLE BY THE MOVABLE MEMBER (8) TO VARY THE LOAD OF THE SPRING MEANS (38, 39) OF THE CONTROL VALVE (30), SO AS TO VARY THE MAINTAINED PRESSURE DIFFERENCE ACROSS THE THROTTLING PORT (11) IN ACCORDANCE WITH THE EXTENT OF OPENING OF THE THROTTLING PORT. 